It's a record-extending eighth UK title for the Englishman, claimed in York two days before he turns 48.
O'Sullivan pulled away in the early stages, taking a 3-0 lead, before Ding brought it back to 4-4 at the break.
A bit more ruthless in the evening session, 'the Rocket' bagged four half centuries and two centuries.
"Each tournament I win and play in, I take great pleasure from," O'Sullivan was quoted as saying by BBC Sport.
"I had to come out and have a good head. There was a big crowd and I wanted to leave blood, sweat and tears on the table. I came out and gave it my all - and I love competing.
"I always keep beating myself up because of the age thing. I keep thinking at some point you have to stop winning, but I am doing all right and I will keep on going until the wheels fall off."